The Museum holds the skull of the Nanotyrannus holotype, a small Late Cretaceous tyrannosaur. Originally described as Gorgosaurus lancensis in 1946, it was reclassified in 1988 in a new genus based on research indicating that the skull bones were fused. Controversy persists about whether it is a juvenile Tyrannosaurus rex or an adult of a pygmy tyrannosaur species. Due to the current housing of the fossil specimen, the underside of the skull was unable to be scanned. Small portions of the lower jaw have been partially reconstructed using an unpainted cast.